Semiconductor device, optoelectronic board, and production methods therefor

ABSTRACT

The semiconductor device of the present invention comprises an optical transmission region, and a light receiving part for converting light propagating through the optical transmission region to an electrical signal, wherein the optical transmission region comprises a two-dimensional optical waveguide layer, and wherein at least a portion of the light receiving part is embedded in the optical transmission region, whereby the present invention can provide a semiconductor device having reduced direction dependency when light propagating through the optical transmission region is received.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor device in which anoptical transmission medium and a light-receiving element carrying outphotoelectric conversion are mixed and mounted, and more particularly,to an optoelectronic device comprising a two-dimensional opticalwaveguide as an optical transmission medium. The present inventionfurther relates to an optoelectronic wiring substrate comprising anelectric wiring layer and an optical transmission layer. Furthermore,the present invention relates to a spherical device.

2. Related Background Art

For cellular phones and personal digital assistants (PDA) which arespreading at a remarkable pace in recent years, there are demands thatthese devices be smaller, lighter and provided with transistors capableof extremely high-speed processing.

It has been pointed out that as the processing speed of transistorsincreases, or as the clock frequency of the CPU increases, the influenceof transmission delay in the electronic circuit substrate alsoincreases. Since the transmission delay is proportional to a product ofa wiring resistance by a wiring capacitance, it is necessary to reducethe wiring resistance or the wiring capacitance. The simplest way toprevent the transmission delay is to minimize a wiring distance withineach chip or between chips.

On the other hand, the processing speed is expected to improve as thewiring distance becomes shorter, but another problem becomes apparent.That is the problem of EMI (ElectroMagnetic Interference). Sinceelectronic parts are placed closer to each other, a wiring distancebecomes shorter but a wiring density becomes higher. As a result, whenhigh-speed signals flow through adjacent signal lines, mutualelectromagnetic induction causes electromagnetic waves to interfere witheach other and generate noise, making it impossible to transmit signalscorrectly.

There are an increasing number of cases where in particular mobileterminals are driven with a larger current than conventional ones underthe influence of proceeding devices operation at a lower voltage,thereby raising concern that influences of EMI becomes larger.

A method of using an optical wiring having an inherent advantage ofcausing no electromagnetic induction is proposed to solve the EMIproblem.

For example, Japanese Patent Application Laid-Open No. 2000-235127discloses a circuit substrate integrating an electronic element and anoptical element as shown in FIG. 35. In FIG. 35, reference numeral 5201denotes an electronic integrated circuit substrate; 5204, a lightemitting part; 5206, a light receiving part; 5207, an optical pathchange section; 5210, a contact electrode. Reference numeral 5211denotes polyimide to bond the circuit substrate 5201 and the lightemitting part or light receiving part. Reference numeral 5212 denotes anelectric wiring; 5213, plane light emitting laser; 5214, a photodiode;5215, a low reflection film; 5216, a polymer layer; 5217, a first cladlayer; 5218, a core layer; 5219, a second clad layer; 5220, a highreflection film.

The light emitted from the light emitting part 5213 is reflected by theoptical path change section, propagates through the core layer 5218 inthe direction indicated by an arrow 5221 in FIG. 35, the light path ischanged again and the light is received by the light receiving part5206. When the propagation direction of the incident light ispredetermined, it is possible to replace a part of the electric signalwiring in the configuration shown in the above-described FIG. 35 with anoptical wiring.

However, when the incident light that propagates through the core layer5218 is the light from the direction 5222 indicated by the arrow in FIG.35, it is impossible for the configuration shown in FIG. 35 to receivethe light.

SUMMARY OF THE INVENTION

Therefore, it is an object of the present invention to provide asemiconductor device with reduced direction dependency when lightpropagating through the optical transmission region is received. It isanother object of the present invention to provide a light emittingdevice or light receiving device capable of contributing to reduction ofdirection dependency (directivity).

The optoelectronic device according to the present invention is anoptoelectronic device comprising an optical transmission region and alight receiving part that converts the light propagating through thelight receiving part to an electric signal, wherein the opticaltransmission region includes a two-dimensional optical waveguide layer,and wherein at least a portion of the light receiving part is embeddedin the optical transmission region.

The present invention can reduce direction dependency of light receivingsensitivity when the light propagating through the optical transmissionregion is received.

The present invention also allows the electric wiring layer to bestacked on the optical transmission layer region. The electric wiringlayer can also be stacked on the entire surface of the opticaltransmission region. Of course, a semiconductor chip including electricwiring can also be stacked. In that case, the above-described lightreceiving part is interposed between the semiconductor chip and opticaltransmission region. In the case where the light receiving part has a pnjunction region in pn structure or a pi or in junction region in pinstructure, at least a part of the junction region is preferably embeddedin the optical transmission region. Of course, substantially all of thejunction region may be embedded in the optical transmission region.

The above-described light receiving part may also be embedded in theabove-described optical transmission region so that the lightpropagating through the two-dimensional optical waveguide layer can bereceived directly.

The above-described light receiving part may also be embedded so thatthe light propagating through the two-dimensional optical waveguidelayer can be substantially received without directivity.

It is preferred that the portion of the above-described receiving partembedded in the above-described optical transmission region have aspherical surface.

The above-described light receiving part may also include a sphericaldevice. A portion of the light emitting part for transmitting light tothe above-described optical transmission region may also be embedded inthe above-described optical transmission region.

It is also preferred that the above-described optical transmissionregion is interposed between the electric wiring layer located on theabove-described optical transmission region and another electric wiringlayer located under the above-described optical transmission region, andat least portions of both electric wiring layers be electricallyconnected through a via hole that penetrates the above-described opticaltransmission region.

It is also possible to perform at least one of O/E conversion and E/Oconversion between the electronic device provided on the above-describedelectric wiring layer and the above-described optical transmissionregion by using the spherical device.

Furthermore, the optoelectronic board according to the present inventionis a substrate in which an electronic device and an optical device arearranged, comprising at least two layers consisting of the first layerand the second layer, wherein the above-described electronic device, theabove-described optical device and an electric wiring that couples thesetwo devices formed in the first layer of the substrate, and atwo-dimensional optical waveguide is formed in the second layer of thesubstrate, wherein the above-described optical device includes a lightreceiving part that receives optical waveguided through theabove-described two-dimensional optical waveguide, and wherein at leasta portion of the above-described light receiving part is embedded in theabove-described two-dimensional optical waveguide.

The above-described two-dimensional optical waveguide can also have asheet form. The above-described light receiving part may have aspherical structure, be mounted from the surface of the above-describedsubstrate so that the light receiving part is embedded in theabove-described optical waveguide and coupled with the above-describedelectric wiring on the surface of the above-described substrate.

The above-described optical device may also include a light receivingpart and an electric circuit that drives the optical device or amplifiesan electric signal obtained.

The light source of the above-described optical device may have aspherical shape, be mounted from the surface of the above-describedsubstrate so that the light source is embedded in the above-describedoptical waveguide of the above-described substrate and coupled with theabove-described electric wiring on the surface of the above-describedsubstrate.

The above-described substrate may also include a spherical-structuredtransmission device for transmission and a parallel signal line, theoutput terminal of the parallel signal line may be coupled with theabove-described spherical transmission device, and parallel/serialconversion may be conducted by the above-described transmission deviceand a serial optical signal can be sent to the above-describedtwo-dimensional optical waveguide.

The optoelectronic board according to the present invention can also becharacterized in that the above-described serial optical signal isreceived by the above-described light receiving part embedded in theabove-described optical waveguide, converted to an electric signal,serial/parallel-converted by an electronic circuit simultaneously formedon the light receiving part and transmitted to the above-describedparallel signal line.

The above-described optoelectronic board may also be constructed with aflexible substrate material (flexible sheet).

The optoelectronic integrated circuit according to the present inventionis an optoelectronic integrated circuit which integrates an electronicdevice and an optical device on the surface of a spherical semiconductorsubstrate, characterized in that the above-described optical device is alight receiving element including a multi-layered film containing a pnjunction in the radial direction of the spherical semiconductorsubstrate, and the above-described electronic device has at least a biascircuit that applies a reverse bias to the above-described lightreceiving element and an amplifier that amplifies light received andconverted to an electric signal.

The optoelectronic integrated circuit according to the present inventionintegrates an electronic device and an optical device on the surface ofa spherical semiconductor substrate and is characterized in that theabove-described optical device is a light receiving element including amulti-layered film containing a pn junction in the radial direction ofthe spherical semiconductor substrate, and the above-describedelectronic device includes a bias circuit that applies a forward bias tothe above-described light emitting element.

The optoelectronic integrated circuit according to the present inventionintegrates an electronic device and an optical device on the surface ofa spherical semiconductor substrate and is characterized in that theabove-described optical device is formed by flatting a portion of thesurface of the above-described spherical semiconductor, exposing aplurality of small planes and then stacking a multi-layered filmcontaining a pn junction in the radial direction of the sphericalsemiconductor substrate on the above-described small planes, and theabove-described electronic device has at least a bias circuit thatapplies a reverse bias or a forward bias thereto.

In the steps of flattening a portion of the surface of theabove-described spherical semiconductor substrate, exposing a pluralityof small planes and stacking a multi-layered film containing a pnjunction in the radial direction of the spherical semiconductorsubstrate on the above-described small planes, it is also possible tocover a region other than small planes of the surface of the sphericalsemiconductor substrate with a dielectric film, etc. and selectivelystack the multi-layer film containing the pn junction only on the smallplanes by organic metal epitaxial growth or gas source molecular beamvapor deposition.

The small planes that constitute the flattened portion of theabove-described spherical semiconductor surface may also consist ofcrystalline planes, which are equivalent to one another in terms ofcrystal engineerings or chemically similar to one another.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view illustrating an embodiment of thepresent invention;

FIG. 2 is a schematic sectional view illustrating an embodiment of thepresent invention;

FIG. 3 is a perspective view illustrating the present invention;

FIG. 4 is a schematic sectional view illustrating the present invention;

FIG. 5 is a schematic sectional view illustrating a spherical opticaldevice;

FIG. 6 is a schematic sectional view illustrating the present invention;

FIG. 7 is a schematic perspective view illustrating the presentinvention;

FIG. 8 is a schematic perspective view illustrating the presentinvention;

FIG. 9 is a schematic perspective view illustrating the presentinvention;

FIG. 10 is a schematic sectional view illustrating the presentinvention;

FIG. 11 is a schematic sectional view illustrating the presentinvention;

FIG. 12 is a schematic sectional view illustrating the presentinvention;

FIG. 13 is a schematic sectional view illustrating the presentinvention;

FIG. 14 is a schematic top view illustrating the present invention;

FIG. 15 is a schematic sectional view illustrating the presentinvention;

FIG. 16 is a schematic view illustrating the present invention;

FIG. 17 is a schematic view illustrating the present invention;

FIG. 18 is a schematic perspective view illustrating the presentinvention;

FIG. 19 is a schematic view illustrating the present invention;

FIG. 20 is a schematic view illustrating the present invention;

FIG. 21 is a schematic view illustrating the present invention;

FIG. 22 is a schematic view illustrating the present invention;

FIG. 23 is a schematic sectional view illustrating the presentinvention;

FIG. 24 is a schematic sectional view illustrating the presentinvention;

FIG. 25 is a schematic view illustrating the present invention;

FIG. 26 is a schematic sectional view illustrating the presentinvention;

FIG. 27 is a schematic sectional view illustrating the presentinvention;

FIG. 28 is a schematic view illustrating the present invention;

FIG. 29 is a schematic view illustrating the present invention;

FIG. 30 is a schematic view illustrating the present invention;

FIG. 31 is a schematic top view illustrating the present invention;

FIG. 32 is a schematic sectional view illustrating the presentinvention;

FIG. 33 is a schematic sectional view illustrating the presentinvention;

FIG. 34 is a schematic sectional view illustrating the presentinvention; and

FIG. 35 is a schematic sectional view illustrates a conventionalexample.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the present invention will be explained using FIG. 1below.

In FIG. 1, reference numeral 1000 denotes an optical transmission regionincluding a two-dimensional optical waveguide layer, and 1010 denotes alight receiving part that receives light propagating through the opticaltransmission region. A sectional view taken in the line 2—2 of FIG. 1 isshown in FIG. 2.

As shown in FIG. 2, by embedding at least a portion of the lightreceiving part 1010 in the optical transmission region 1000, it ispossible to provide a semiconductor device having reduced directiondependency of light propagating through the optical transmission regionthat can be received by the light receiving part.

In FIG. 2. reference numerals 1030 and 1040 show a state thatpropagating light is received by the light receiving part 1010.

The optical transmission region is formed of, for example, a core layerinserted between clad layers of a refraction factor lower than that ofthe core layer. As the material of the core layer, optical resin such asPMMA, polymethyl methacrylate, silica-based glass and plastic materialsuch as polystyrene and polycarbonate, etc. The material of the cladlayer is not particularly limited if it has at least a refraction factorlower than that of the core layer. For example, a polymer containingfluorine, PCZ and Arton (manufactured by JSR Company) can be used.

Unlike a linear optical waveguide which presets the direction of lightpropagation to a single direction, the two-dimensional optical waveguidelayer means a planar optical waveguide capable of propagating light in aplurality of directions within the plane. In the present invention, thetwo-dimensional optical waveguide layer is also sometimes referred to as“optical sheet”. The light receiving part is a photoelectric conversiondevice capable of performing O/E conversion. A pn type or pin typephotodiode can be used. The pn junction plane can be either parallel tothe optical sheet or almost perpendicular to the optical sheet. It isparticularly preferred that the shape of the part embedded in theoptical transmission region of the light receiving part be polyhedral orspherical.

When the light receiving part is embedded in the optical transmissionregion, either a portion or substantially the whole of the lightreceiving part can be embedded. It is preferred that the pn junctionsection be embedded at least in the core layer.

When the optical transmission region includes the core layer and cladlayer, it is preferred that the light receiving part be embedded to sucha depth that it reaches the core layer.

It is also possible to form an electrical wiring region on thetwo-dimensional optical waveguide layer which is the opticaltransmission region. Its example is shown in FIG. 3.

In FIG. 3, reference numeral 1101 denotes an optoelectronic board; 1102,a two-dimensional optical waveguide layer (hereinafter referred to as“optical sheet”) formed therein. Reference numerals 1103 and 1106 denoteelectronic devices formed on an electric wiring region 1108 (e.g., CPU,RAM, RF oscillator); 1104, electric wiring formed on the surface; 1105indicated by an arrow in FIG. 3, optical wiring formed by light thatpropagates through the above-described optical sheet. Reference numeral1109 denotes a support substrate. The support substrate, of course, canbe provided as required. Or the support substrate itself can function asa clad layer.

FIG. 3 shows a state that a signal is transmitted from the electronicdevice 1106 to another electronic device 1107, etc. by using the opticalsheet.

For example, when wiring from the electronic device 1106 to 1107 isperformed by means of optical wiring, an electric signal from theelectronic device 1106 is converted to an optical signal by an E/Oconversion section (not shown) and this optical signal is spread overthe optical sheet 1102. The optical signal propagates in a radialpattern and in all directions, but it is also possible to allow theoptical sheet to have a function so that the optical signal mainlypropagates in a specific direction.

The optical signal that propagates through the optical sheet is receivedby the electronic device 1107 via an O/E conversion section (not shown).Optical wiring is realized in this way.

Furthermore, since the two-dimensional optical waveguide layer is used,even if the electronic device 1107 does not exist in an initial circuitpattern, the electronic device 1107 can be placed at any position of theelectric wiring region 1108 (e.g., FIG. 1). Though it can be placed atany position, of course, an empty region is necessary to place theelectronic device 1107. Use of optical wiring can reduce influences ofEMI and since at least a portion of the light receiving part is embeddedin the optical waveguide, it is possible to receive signal lights fromvarious directions.

Furthermore, it is further preferred that at least a portion of thelight emitting part which sends signal light to the optical sheet beembedded in the optical sheet. Its example is shown in FIG. 4. FIG. 4describes a case where an electronic device is mounted as a flip chip.Reference numeral 1103 denotes the electronic device; 1104, a metalwiring region; 1201, a light receiving part; 1202, a metal bump; 1205,an upper clad layer; 1206, a core layer; 1207, a lower clad layer; 1208,a light emitting part. Reference numeral 1210 shows a state thatpropagating light is received by the light receiving part 1201.Reference numeral 1203 shows a state that an electric signal obtained byO/E-converting the light received by the light receiving part istransmitted to the electronic device. Reference numeral 1211 shows astate that light propagating from the light emitting part 1208 throughthe core layer 1206 is transmitted.

In FIG. 4, since a portion of the light emitting part 1208 is embeddedin the core layer 1206 and a spherical device (will be described indetail later) is used, light propagates in such a way that it spreads indirections within the plane in the core layer.

A ball IC is produced, for example, as follows:

-   (1) First, an Si sphere is made. Granular polycrystalline Si is    melted inside a pipe with a diameter of 2 mm to form a    quasi-spherical single crystal. After this, surface polishing is    applied in a procedure similar to that for producing a ball bearing    to make a complete sphere of 1 mm.-   (2) Then, the sphere is passed through an IC process pipe and    subjected to oxidation and diffusion processes. Pattern printing can    be provided using a method disclosed, for example, in Japanese    Patent Application Laid-Open No. 10-294254 and Japanese Patent    Application Laid-Open No. 11-54406. According to the former, a    circuit pattern corresponding to the spherical surface of the Si    sphere material is provided, the circuit pattern is exposed over a    region more than half of the total spherical surface all at once. In    the latter, an axis passing through the center of the spherical IC    is determined arbitrarily, the spherical IC is rotated around the    axis intermittently, the exposure region of the surface of the    spherical IC corresponding to this rotation angle is exposed using a    mask corresponding thereto. An Si ball IC is completed in these    steps. When light is emitted from or entered into the    two-dimensional optical waveguide effectively, it is also possible    to additionally use a mirror, prism, grating or hologram, etc.

The spherical semiconductor material used for the present invention caninclude Si, GaAs, InP, GaN, SiGe, GaAsN, Ge, AlN, etc. Of course, it ispreferred that these materials be single crystals, but if thesematerials serve as the light receiving part or light emitting partsufficiently, these materials may be polycrystalline or amorphous. Themulti-layer film for forming the above-described light receiving elementor light emitting element can be composed of, for example,p-Si/i-Si/n-Si, p-GaAs/GaAsN/n-GaAs or p-(Al, Ga) (As, P, N)/i-(Al,Ga)(As, P, N)/n-(Al, Ga)(As, P, N) layers. Here, with respect to anexpression “(A, B)(C, D, E)”, A and B means elements belonging to theGroup III of the Periodic Table, and C, D and E means elements belongingto the Group V of the Periodic Table. Accordingly, the expression “(A,B)(C, D, E)” means “A_(x)B_(1−x)C_(y)D_(z)E_(1−y−z)”.

Embodiment 1: Optical Sheet+Spherical Light Receiving Device

A first embodiment will be explained using FIG. 1, FIG. 2, FIG. 5 andFIG. 6. As the core layer of the optical transmission medium 1000,optical resin PMMA was used. As the clad layers between which the corelayer is inserted, polyimide was used. The thickness of the entireoptical transmission medium was approximately 0.8 mm (the core layer:0.2 mm; the clad layer: 0.3 mm×2), the size is 30×30 mm. The specificmethod of manufacturing the optical transmission medium will bedescribed later.

As the light receiving part 1010, a spherical device can be used. FIG. 5shows a schematic sectional view of the spherical device. In FIG. 5,reference numeral 1501 denotes a spherical p-type Si member. The Sisphere itself is obtained, for example, by melting granularpolycrystalline Si, transforming it into a quasi-spherical singlecrystal, applying surface polishing to make a complete sphere using aprocedure for making a ball bearing. On the spherical Si member 1501,p-type AlGaAsN is allowed to grow as a first clad layer 1502, undopedGaAsN as an active layer 1503, and n-type AlGaAsN as a second clad layer1504. A GaAsN-based compound semiconductor is used here because its bandgap is smaller than that of GaAs and it has an excellent temperaturecharacteristic and facilitates lattice matching.

Of course, instead of allowing a compound semiconductor thin film togrow on the spherical Si, it is also possible to allow an n-type siliconthin film to grow on the surface of p-type spherical silicon and form apn junction to produce a light receiving part (photodiode). Moreover, itis also possible to use an ion implantation method or diffusion method(thermo-diffusion or solid phase diffusion) instead of producing a pnjunction by means of growth of a thin film.

At an electrode section of this ball IC, a cathode 1504 and an anode1505 are formed, the anode being electrically connected to the cathodevia a via hole 1506. The via hole 1506 can be formed by etching or laserbeam machining.

The light receiving part 1010 is then embedded in the opticaltransmission medium. More specifically, it is embedded to such an extentthat it reaches the clad layer 1605 and core layer 1606 as shown in FIG.6. Reference numeral 1607 denotes a clad layer.

To embed the light receiving part, a cavity corresponding to theembedding region needs to be made in the optical transmission medium.The cavity corresponding to the light receiving part is formed byheating a metal die for boring and pressing it against the opticaltransmission medium. The semiconductor device of the present inventionis completed by embedding the light receiving part 1010 in the cavityformed. By applying a reverse bias between the cathode 1504 and anode1505, the light incident upon the light receiving part 1010 is absorbedby the pn junction and obtained as an electric signal.

As explained above, a semiconductor device with significantly reduceddirection dependency (directivity) of light propagating through theoptical transmission medium is produced in this way. Moreover, the lightreceiving part can directly receive light that has propagated throughthe optical transmission region.

A spherical device has been used as the light receiving part, but thelight receiving part is not limited to a spherical device and can haveany shape if it can at least be embedded in the optical transmissionmedium, for example, a normal photodiode having a pn junction.

It is also possible to form not only the light receiving part but alsolight emitting part by using the spherical device and embed portionthereof in the optical transmission medium. It is further possible toform an electric wiring layer over the entire optical sheet. It is alsopreferred to provide the above-described optical sheet under theelectric wiring printed substrate and form an optical wiring in place ofa portion of the wiring as required.

Embodiment 2: Method of Adding Electronic Device

In view that the present invention reduces direction dependency of thelight receiving part, the following method of adding electronic devicecan be used.

This embodiment will be explained referring to FIG. 7 to FIG. 9. In FIG.7, reference numeral 1750 denotes an optoelectronic board. Referencenumeral 1700 denotes an optical transmission medium; 1707 and 1705,electronic devices. The electronic device 1705 is provided with a lightemitting part (not shown) capable of propagating signal light to theoptical transmission medium 1700. Reference numeral 1720 denotes anelectric wiring layer (e.g., a printed substrate).

When a new electronic device 1706 is added to an empty region 1730 ofthe optoelectronic board 1750, if no optical transmission medium isprovided, it is only possible to merely add the electronic device 1706and carry out electric wiring between the individual devices. However,in the case of the optoelectronic board 1750, it is possible to useoptical wiring, for example, between the electronic devices 1705 and1706. In FIG. 7, reference numeral 1780 denotes the light receiving partmade according to the above-described method.

The optical transmission medium 1700 is provided beforehand withcavities for embedding as shown in FIG. 8. The number of cavities forembedding can be one or plural. It is preferred that a plurality ofcavities be made beforehand from the standpoint of the degree of freedomof layout. For example, it is possible to form an array of cavities. InFIG. 8, reference numeral 1741 denotes a cavity for embedding the lightemitting part of the electronic device 1705. Unused cavities 1742 and1744 can be filled with resin, etc. This is effective when lightpropagating through the optical transmission medium is scatteredunnecessarily by unused cavities. It is also preferred to provide adifference in the etching characteristic between the resin that fills acavity and its periphery to make it easier to remove the filler of thecavity.

This embodiment uses a cavity 1740 to add the electronic device 1706 anda cavity 1743 to add the electronic device 1707.

As shown in FIG. 9, a region where the electronic device 1706 is addedis removed and the cavity 1740 is exposed. Reference numeral 1760denotes the removed part. Of course, such a process can be omitted ifthe electric wiring layer 1720 is not formed in the region 1730 shown inFIG. 7. Then, if the cavity 1740 is filled with some filler, this isremoved by etching, etc. Then, the device is added in such a way thatthe light receiving part 1780 of the electronic device 1706 is embeddedin the cavity 1740. Since the electronic device 1705 has the lightemitting part, it is possible to connect between portions of theelectronic devices 1705 and 1706 by optical wiring using the opticaltransmission medium 1700 which is not used until the electronic device1706 is added.

When a new device is added to an extremely small printed substrate suchas built in a cellular phone, this embodiment allows optical wiring tobe used and makes it possible to reduce influences of EMI caused by theaddition of the electronic device.

When a new electronic device is added assuming that the existing wiringpattern is used, the existing circuit group may be affected by EMIcaused by the merely added electronic device. In such a case, opticalwiring can be used as in the case of this embodiment.

When a linear waveguide is formed beforehand according to the positionof the newly added electronic device, optical wiring in theconfiguration shown in FIG. 35 can also be used. But this significantlyreduces the degree of freedom of layout. This is because the locationwhere the new device is added is dependent on the location of the linearwaveguide formed beforehand. Use of a two-dimensional optical waveguideas in this embodiment allows optical wiring with high degree of freedomof the device layout.

Embodiment 3: Photoelectric Two-layer Substrate+Spherical Light I/ODevice

FIG. 3 is a schematic perspective view for illustrating this embodimentof the present invention.

In FIG. 3, reference numeral 1101 denotes an optoelectronic board; 1102,a two-dimensional optical waveguide layer (hereinafter referred to as“optical sheet”) formed inside the optoelectronic board; 1103, 1106 and1107, electronic devices formed on the surface of the optoelectronicboard (e.g., CPU, RAM, RF oscillator); 1104, electric wiring formed onthe surface; 1105, optical wiring formed by light that propagatesthrough the above-described optical sheet.

First, the method of producing the optical sheet will be explained.

The structure of the optical sheet is not limited to a particularstructure if it can transmit light for at least a predetermineddistance, and it is preferred that the structure satisfies the followingconditions.

-   (1) The optical sheet can have a two-dimensional slab type optical    waveguide for guiding light.

It is preferred that the propagation loss of the optical sheet is assmall as possible but the propagation loss depends on the transmissiondistance. For example, for transmission loss of 0.1 dB/cm, a substrateof several cm per side can be used.

-   (2) Electric wiring can be formed on the surface of the optical    sheet.

This is intended to exploit a conventional electric wiring pattern assuch.

A structure of the optical sheet satisfying the above-mentioned (1) and(2) can be obtained by using PMMA for the support substrate and the cladlayer and by using an organic resin such as polyimide for the opticalwaveguide layer. It is preferred that the optical transmission layer beprovided over the entire surface under the electric wiring layer.

FIG. 4 is a schematic sectional view for showing the portion 4 of FIG.3. The following is an explanation of a case where the electronic device1103 makes an optical interconnection using the optical sheet 1102. FIG.4 illustrates a case where the light receiving part 1201 and the lightemitting part 1208 are separated from the electronic device 1103. Ofcourse, the light receiving part and the light emitting part may also bebuilt in the electronic device 1103 itself.

Reference numeral 1207 denotes a resin substrate (also serves as a cladlayer); 1205, a clad layer; 1206, a core layer of higher refractionfactor than the members 1205 and 1207. The substrate was 0.5 mm thick,the core layer was 0.1 mm and the clad layer was 0.3 mm, but eachthickness is not limited to these sizes.

The optical sheet is obtained by integrating these three layers. It ispossible to make a flexible substrate with high bending strength byusing a flexible PMMA substrate as the substrate, and polyimide resinwhich can be used for coating of the core layer and clad layer.

This embodiment uses an optical I/O device (spherical optical device)formed of a compound semiconductor on a spherical Si substrate.

This spherical optical Si substrate will be explained in brief. (Itemsrelated to the spherical device are described, for example, in JapanesePatent Application Laid-Open No. 12-31190).

FIG. 5 shows a schematic view of the spherical optical device. In FIG.5, reference numeral 1501 is a spherical p-type Si substrate; 1502, aP-type AlGaAsN clad layer; 1503, an undoped GaAsN active layer; 1504, ann-type AlGaAsN clad layer. A GaAsN-based compound semiconductor is usedhere because (1) its band gap is small and it has an excellenttemperature characteristic and (2) it facilitates lattice matching withSi. It is also possible to use other materials including the substrate.

At an electrode section of this ball IC, an anode 1505 and cathode 1504electrically connected to a via hole 1506 are formed. This embodimentuses the light emitting element and light receiving element of the samestructure, but they may have different structures. It is preferred thatthe cathode 1504 have a windowed structure or mesh structure to allowlight to be input/output.

When the ball IC is operated as the light emitting element, carriers areinjected into a pn junction by applying a forward bias between thecathode 1504 and anode 1505, thereby generating light emission. Thelight generated is radiated from the light emitting window in a widerange of angles.

On the other hand, when the ball IC is operated as the light receivingelement, the light incident upon the incident light window from a widerange of angles is absorbed as an electric signal by the pn junction andtaken in by the adjacent electronic device by applying a reverse biasbetween the cathode 1504 and anode 1505.

Both the light emitting device and light receiving device have aspherical surface, and therefore the ability to input/output light witha wide range of angles constitute an outstanding feature of thisembodiment.

The ball IC of this embodiment can be produced not only for the opticalI/O section but also for other ICs simultaneously. The method ofproducing ICs and their exposure method are disclosed in Japanese PatentApplication Laid-Open No. 10-294254 (U.S. Pat. No. 6,097,472) “SphericalDevice Exposure Apparatus and Fabrication Method”, etc.

This embodiment uses a preamp operating on 3.3 V in a CMOS configurationto be used for the light receiving element.

The method of mounting this spherical optical device will be explainedusing FIGS. 10 to 12.

First, a hemispherical cavity is made in the above-described opticalsheet substrate which can allow the above-described ball IC to beembedded. The boring method can be selected arbitrarily. The cavity maybe formed at a predetermined location using photolithography and etchingor the cavity may be formed individually at an arbitrary location usinglaser, etc. This embodiment uses thermal fusion process.

As shown in FIG. 10, metal balls are used as a die 2000, heated andpressed against the above-described resin substrate 1207 (FIG. 11) andhemispherical cavities 2100 are produced (FIG. 12). The depth of thecavities is set such that it reaches the vicinity of the core layer ofthe optical wiring substrate. Of course, it is also possible to dent toan extent that the cavity reaches the lower part of the core layer.

After this process, electric wiring 1104 is printed on the optical sheetas shown in FIG. 4 and then an electronic device represented by an LSIis mounted. Any method can be used for mounting, and in this embodiment,a flip chip mounting method is used.

The optical I/O section is mounted in the cavity of the optical sheet insuch a way that the optical I/O section is arranged on the bottom of thecavity. The optical I/O section is positioned and fixed so that theoptical I/O section is brought into contact with the bottom of thecavity to allow light to be taken in or out (see FIG. 13). Since theoptical I/O section in this embodiment is spherical, strict positioningaccuracy is not required. After the cavity 2100 and spherical device arepositioned, they are fixed by UV hardening resin, etc.

Finally, the spherical optical I/O device and the surface-mountedelectronic device are connected by means of printed electrical wiring.For this, it is preferred to use bump or plating.

FIG. 13 shows an example where a print wiring 1104 and an electrode 1504are connected via a bump 2302.

This embodiment shows an example where a spherical IC is used as the E/Oand O/E conversion section but this embodiment is not limited to thisexample.

Principle of Operation

The principle of operation will be explained below.

First, the transmission function will be explained.

FIG. 4 is an enlarged view of the portion 4 of FIG. 3. In FIG. 4, anoutput electric signal (CMOS logic) of the I/O section of an LSI 1103can be transmitted to an adjacent electronic device via electric wiring1104.

However, it is also possible to generate an output optical signal 1211by directly driving an adjacent optical I/O device (e.g., a sphericaloptical device) and use it as optical wiring via the optical waveguidelayer (optical sheet) 1206. Either method can be selected as required.

A case where an adjacent spherical optical device is driven will beconsidered.

An LSI logic signal (e.g., 3.3 V in the case of CMOS) is a voltageenough to drive the above-described spherical optical device. Byapplying a logic signal as a forward bias to the spherical opticaldevice, the electric signal is converted to an optical signal.

At this time, since light is radiated over the entire spherical surface,light spreads and propagates over the entire surface of the opticalsheet without a special optical system. As a result, it is possible tosecure 80% or more as the efficiency of coupling with the opticalwaveguide.

Then, the reception function will be explained.

When an input optical signal 1210 propagating from an arbitrarydirection of the optical sheet 1206 reaches the surface of the sphericallight receiving element 1201, it is taken in, absorbed near areverse-biased pn junction and converted to an electronic signal. Theconverted electric signal is taken in by the adjacent LSI 1103 andprocessed as the input electric signal 1203. In this case, if a preampfor amplifying the electric signal is integrated on the surface of thespherical optical device, the electric signal can be restored to a CMOScompatible voltage.

Thus, using the present invention can reduce direction dependency of thelight receiving part.

When a plurality of metal wires is placed close to each other, if ahigh-speed data communication is performed (e.g., 1 Gbps), the strengthof nearby electromagnetic noise is expressed by “strength of the noisesource (frequency, waveform, drive current)”×“transfer constant(resonance with power line, coupling with adjacent line)”×“antennafactors (connector, electrode)”.

That is, the longer the wiring length or the greater the current valueor the greater the signal speed or the closer the signal pulse to asquare wave, the higher the noise level becomes.

Therefore, when metal wires are used near the CPU, etc. which requireshigh-speed processing, it is impossible to completely eliminate EMI.

On the other hand, using optical wiring as in the case of thisembodiment can solve this problem. This is because optical wiring isfree of electromagnetic induction and the transfer constant becomeszero.

Above all, as in the case of this embodiment, by separating and placingthe electric wiring layer and optical transmission layer as two layersand using a two-dimensional optical waveguide (optical sheet) as theoptical transmission layer, it is possible to provide an optoelectronicwiring substrate which prevents influences of EMI caused by a specificdevice and also facilitates the production process.

On the other hand, the physical dimensions required for wiring peroptical wire when the optical waveguide (so-called one-dimensionalwaveguide) is used are greater than electric wiring by one or moreorders of magnitude. Therefore, changing all electric wiring to opticalwiring increases demerits such as increasing the size and increasingloss by bending, etc.

Furthermore, there is also a demerit that introducing optical wiringmakes it unavoidable to change conventional electric wiring patterns.

This embodiment solves the above-described two demerits by using atwo-dimensional optical waveguide (optical sheet) as the opticaltransmission layer. Applying a two-dimensional optical waveguide(sheet-shaped optical waveguide) to the optical waveguide which providesoptical wiring increases the degree of freedom of layout. Furthermore,when light is transmitted from the light emitting part to the opticalsheet, it is possible to two-dimensionally transmit optical data fromthe light emitting device in all directions.

Furthermore, it is desirable that the light emitting device connectableto the two-dimensional optical waveguide can emit light in alltwo-dimensional directions and that the light receiving device canreceive light from all two-dimensional directions. Examples of theabove-described devices include optical devices formed on a sphericalsurface.

When the light receiving element with a spherical surface is used, it ispossible to design the device so that it can receive light from alldirections. This appears as an effect of drastically relaxing themounting accuracy when light from a waveguide whose propagationdirection is fixed is taken in.

By building an amplifier circuit into the bias circuit in the sphericaloptical device, it is possible to operate this single spherical opticaldevice as the optical I/O element. This makes it possible to reduceinfluences on the conventional design of electronic circuits and realizeoptical interconnection.

Embodiment 4: Clock Distribution

An application example of the present invention will be explained below.

FIG. 3 shows a case where a plurality of electronic parts (CPU andmemory, etc.) 1103 are mounted on one substrate 1101 and a portion ofthe wiring is coupled with the substrate through the spherical opticaldevice 1201 as in the case of Embodiment 3.

In FIG. 3, the LSI 1106 is a clock generator. At this time, a clocksignal is sent to the optical waveguide of the optoelectronic board viathe spherical optical device 1208 (FIG. 4). The signal for which opticalwiring is selected is output to the spherical optical device and isdriven by the signal sent by the CMOS itself. No special driver isrequired. For this reason, a GaAsN-based semiconductor laser whichoperates on a low voltage is used as the optical device.

The spherical optical device 1208 converts the clock signal to light anddistributes the clock signal converted to the optical signal to alldevices on the substrate. Since any electronic device (e.g., MPU 1103)on the substrate is provided with the spherical optical device 1201, itreceives the optical signal from the clock generator 1106. Since thespherical optical device 1201 has a spherical shape, it can receivelight from any direction with high light receiving efficiency.

The light received is separated into pairs of electrons and holes, withthe electric signal being amplified by a preamp formed on the sphericaloptical device of an adjacent LSI and taken in by the MPU. Other devices(e.g., RAM) can also receive the clock signal using a similar method andtherefore these devices can also be operated with a common clock.

Conventionally, when a clock signal is distributed to individualdevices, wiring patterns cannot be selected freely or wiring distancescannot be equalized, and therefore it is not possible to ignoreinfluences of EMI caused by transmission delay and high-speed, largecurrent operation. However, according to this embodiment, optical wiringwith the shortest distance and with no electromagnetic induction can becarried out to solve these problems all at once.

Embodiment 5: MPU→Memory (Serial Transmission)

Then, another application example will be explained.

FIG. 14 is a schematic view for illustrating another embodiment of thepresent invention. In FIG. 14, reference numerals 2407 and 2408 denotetwo CPUs. Reference numeral 2409 denotes a RAM shared by these two CPUS(2407, 2408). In FIG. 14, reference numeral 2401 denotes electric wiringfor parallel transmission, and 2402 denotes optical wiring ring forserial transmission. Reference numeral 2403 denotes LSIs.

Normal electric wiring requires, for example, 64-bit data wires 2401with 6 transmission paths.

In applications (moving images) of sending large-volume data at highspeed, data may not be correctly sent using conventional wiring for theabove-described reasons (transmission delay and EMI). In such cases,optical wiring can be used. Specifically, a part or all of signaltransmission between CPUs (2407, 2408) and RAM 2409 is carried out usingthe optical wiring 2402.

Further, in FIG. 14, in order to send data from the MPU to the memoryusing 64 bits, 6 electric wires are necessary, but performingparallel/serial conversion at the final stage of the MPU and connectingone optical I/O element allows the electric signal to be transmitted asan optical signal through the optical waveguide of the optoelectronicboard, received by the optical I/O element on the receiving side andconverted from serial to parallel, resulting in a 64-bit parallelsignal.

When the optical signal is converted from parallel to serial, the clockbecomes higher, but since the signal propagates through the opticalwaveguide, there is no problem of EMI.

This embodiment selects optical wiring from the beginning, but it is notalways necessary to use only optical wiring. That is, by allowingelectric wiring paths to also be selected, it is possible to sometimesconnect electric wiring and sometimes connect optical wiring. Thisflexibility is one of the features of the present invention.

In the case of electric wiring, wiring may be performed in such a way asto bypass other devices to avoid EMI, resulting in an increase of thewiring length, causing transmission delay and distortion of waveforms.Selecting optical wiring at this time makes it possible to provideshortest EMI-free connections, which in turn prevents transmission delayand distortion of waveforms.

The final decision as to which signal should be applied to electricwiring or optical wiring is made by the device that controls the bus.

The converted light spreads and propagates through a two-dimensionaloptical waveguide and reaches an IC located in another place. Near thisIC, a ball IC for O/E conversion is also placed. This embodiment placesthe same ball IC. Since it has a spherical surface, light directly hitsthe pn junction surface without using any prism or mirror, etc., whichprovides an extremely easy way of mounting.

Embodiment 6: Integrating Pin-PD and Amp on Ball Si

FIG. 15 is a schematic view for illustrative another embodiment of thepresent invention. In FIG. 15, reference numeral 2508 denotes aspherical Si substrate and its northern (upper) hemisphere shows thesurface and its southern (lower) hemisphere shows a sectional view.Reference numeral 2509 denotes a light receiving element formed on thesouthern hemisphere: 2503, an IC such as a bias circuit that drives thelight receiving element or a preamp that amplifies an electric signal.Reference numeral 2510 denotes a optical waveguide substrate: 2506, acore layer: 2505, a clad layer: 2516, an electrode: 2512, printedwiring: 2504, a bump; 2511, output light; 2507, input light.

The method of producing the semiconductor device shown in FIG. 15 willbe explained below.

First, as shown in FIG. 16, a p-Si layer 2521, i-Si layer 2509 and n-Silayer 2520 are formed on almost half (southern hemisphere) of an undopedspherical Si substrate 2601 (diameter: about 1 mm) by ion implantationto form a light receiving element region. The depth is around 0.3 μm.Crystal recovery is performed through annealing processing as required.

Then, as shown in FIG. 17 (the upper half of the sphere expresses thespherical surface and the lower half expresses a section of the sphere),a bias circuit 2701 for applying a reverse bias to this light receivingelement, a preamp circuit 2702 for amplifying the electric signalconverted from the optical signal to a desired voltage level, and awaveform shaping circuit 2703, etc. are formed on the remainingspherical surface region (northern hemisphere). Reference numeral 2704denotes electric wiring, 2705; a light receiving element electrode;2506, an electronic circuit electrode. Since the electrodes 2705 and2706 are the electrodes for applying voltage to the p-Si layer 2521 andn-Si layer 2520 respectively, the potential of the electrode 2705 isprevented from being applied to the n-Si layer 2520.

Here, all electronic circuits use a 3.3 V CMOS logic circuit. At thesame time, all electronic circuits form a positive electrode 2705 andnegative electrode 2706 of the light receiving element and a wiringpattern 2704. Furthermore, reference numeral 2506 denotes an externalelectrode for input/output of the electronic circuit.

An example of the mounting method will be shown below. In FIG. 15, forexample, reference numeral 2510 denotes a clad layer made of PMMA whichalso serves as a substrate; 2506, a (sheet-shaped) core layer whichserves as a optical waveguide; 2505, a clad layer.

Photosensitive polyimide, etc. is applied to form the core layer 2506and clad layer 2505, and a cavity for fitting therein is made to allowthe spherical optoelectronic device of the present invention is formedby using a photolithography technology, etc. After a desired wiringpattern is printed thereon, the optoelectronic device of the presentinvention is fixed with UV-hardened resin (not shown).

After this, as shown in FIG. 18, contact is made between the wiringpattern 2803 and the electrode 2506 on the device using an Au bump 2804,etc. In this process, plating may also be used instead of the bump.

In FIG. 18, 2401 denotes a clad layer, and reference numeral 2402denotes the optical waveguide core layer.

The principle of operation will be explained below.

In FIG. 15 or FIG. 17, a reverse bias (e.g., 3.3 V) is applied to the pnjunction of the optoelectronic device through the bias circuit 2701. Atthis time, this optoelectronic device can receive the optical signalpropagating through the two-dimensional optical core layer 2506 from anarbitrary direction. This is because at least a portion of the lightreceiving part is embedded in the optical transmission medium.

The input optical signal is taken in, absorbed near the reverse-biasedpn junction and converted to an electronic signal. The convertedelectric signal is amplified as the input electric signal by theadjacent preamp 2702 to a CMOS logic level, processed by a waveformshaping circuit 2701, etc. and sent to the printed wiring contacted viaa bump.

From the above-described embodiments, it is possible to (1) receivelight from any two-dimensional direction, (2) amplify or shape thewaveform using an integrated electronic circuit, and (3) facilitatemounting. Furthermore, it is possible to (4) reduce influences onexisting electronic circuits and allow a single device to serve as anoptical interconnection I/O.

Embodiment 7: III-VN on Ball GaAs

This embodiment uses a spherical GaAs substrate instead of a sphericalSi substrate.

The production method of this embodiment will be explained using FIG.19.

From the surface of a high-purity undoped spherical GaAs substrate 2901,a p-type GaAs layer 2902, a GaAsN light-absorbing layer 2903 and ann-type GaAs layer 2904 are formed by means of ion implantation.

The concentration of p-type impurities is about 1E19 cm⁻³ and theconcentration of n-type impurities is about 1E18 cm⁻³ (ion type can bedetermined arbitrarily). The undoped GaAsN is obtained by applying ionimplantation of high concentration N to GaAs (e.g., 1E21 cm⁻³). RTA(Rapid Thermal Annealing) is effective to eliminate damage during ionimplantation.

With regard to the implantation depth, the ion implantation condition ofother layers is set in such a way that the thickness of the GaAsN layeris 0.2 μm.

The subsequent processes and mounting process are in conformance withEmbodiment 6. With regard to the electronic circuit section, using abipolar process makes it possible to make an electronic circuit having afunction equivalent to or higher than Embodiment 6. For the electrode, amesh structure can also be used instead of a complete window structure.

This embodiment will be explained focused on differences from Embodiment6. The operation as a light receiving device of this embodiment is thesame as in the case of Embodiment 6. That is, by applying a reverse biasto the p-GaAs layer 2902 and n-GaAs 2904 in FIG. 19, the light incidentupon the incident light window from a wide range of angles is absorbedby the pn junction and taken in as an electric signal by an adjacentelectronic device. Since GaAsN has a smaller band gap than GaAs, GaAsNoperates on a lower voltage than GaAs.

Furthermore, GaAsN has a greater mobility than Si, and can thereforerespond fast. Reference numeral 2903 denotes an i-GaAsN layer.

Since GaAsN is a direct transition type compound semiconductor, it canalso be used as a light emitting element. When GaAsN is operated as alight emitting element, by applying a forward bias to the electrode 2705and 2706 in FIG. 15 or FIG. 17, the light emitted at the pn junction isradiated from the light emitting window in a wide range of angles. Thismay be driven by the logic data itself or driven through a drivercircuit.

Since the surface of both the light emitting device and light receivingdevice is spherical, this embodiment has a major feature of beingcapable of letting in and out light in a wide range of angles.

Embodiment 8: GaAsN Films on Facets of Ball Si

FIG. 20 is a schematic view for illustrating another embodiment.

In this embodiment, GaAsN/AlGaAsN is stacked on a ball Si substrate tobe used as a light emitting element or light receiving element.Reference numeral 3101 denotes a spherical semiconductor substrate;3102, an IC; 3103, an optical device; 3104, a bump; 3105, a opticalwaveguide substrate; 3106, a core layer; 3107, a clad layer; 3108,printed wiring; 3109, output light; 3110, input light. The productionmethod will be explained below.

Production of Ball IC

As shown in FIG. 21, the IC 3102 is formed on the hemispheric surface(here, northern hemisphere) of an undoped spherical Si substrate (1 mm)3101. This IC may be a drive IC or parallel-serial conversion circuit inthe case where this IC is a light emitting element. This IC is a biascircuit, preamp, waveform shaping circuit or serial-parallel conversioncircuit in the case where this IC is a light receiving element. Ofcourse, when the IC is used for both functions, appropriate electroniccircuits need to be added. These circuits can be made through a normalCMOS process and its logic voltage is 3.3 V. Reference numeral 3111denotes electric wiring.

Production of Optical Device

After the Si ball IC process is almost completed, an optical device isproduced. First, the entire sphere is covered with a nitride film (SiN),etc. and the region where the optical device is made is ground andpolished to form a smooth surface. The sphere is covered with thenitride film to protect the electronic device during the optical deviceprocess and to be used as a selective growth mask. It is desirable toform a film with small stress (here, Si₃N₄ (200 nm thick) is used) tocover the spherical surface.

As the region for producing the optical device, this embodiment usesplane (111) and planes associated therewith (four planes in total;(100), (010), (−100), (0-10)) 3301 (triangular plane approximately 20 μmper side) in the southern hemisphere. FIG. 22 is a plan view of FIG. 21viewed from the S-pole of the sphere and reference numeral 3101 denotesthe spherical substrate and 3301 denotes the (111) equivalent plane.

FIG. 23 is a sectional view of one of these planes. The entire surfacemay be covered with a nitride film, etc. again if necessary and a windowis made only in the region for producing the device. Since selectivegrowth takes place according to the shape of the opening, thisembodiment controls the opening so that it becomes cylindrical.Reference numeral 3101 denotes the spherical semiconductor substrate;3301, the plane (111); 3401, the SiN film. Here, the (111) equivalentplane is selected for the following reasons.

-   (1) Because they are chemically equivalent to each other, it is    possible to make a uniform structure in the subsequent crystal    growth. (If another crystalline plane is included, anisotropy occurs    in aspects of composition, film thickness and direction of crystal    growth.)-   (2) In the plane contacting S-pole (in the light propagation    direction), light is emitted in at least four directions or light is    received from at least four directions. (This is not limited to    the (111) equivalent plane provided that other planes have an    equivalent function or higher function.)    Crystal Growth

The structure of the device will be explained using FIG. 24. First,GaN_(x)As_(1−x) is stacked as a buffer layer 3501 on only a selectedregion (opening part) using a gas source MBE (molecular beam epitaxy)method or MOCVD (metal-organic chemical vapor deposition) method. Thegrating constant at this time can be selected as appropriate accordingto the conditions of the clad layer and active layer.

Here, after the nitrogen composition X is changed gradually from 0.2 to0 so that it provides lattice matching with In_(0.1)Ga_(0.9)As, InGaAsis further stacked while changing the In composition gradually. Afterthis, the n-InAlGaAs clad layer 3502, GaInNAs/InAlGaAsMQW (MultipleQuantum Well) active layer (light emitting wavelength: 1.3 μm) 3503,p-InAlGaAs clad layer 3504 and p-InGaAs contact layer 3505 are stackedone after another. A positive electrode 3506 is formed after a lightinput/output window 3507 is attached. Then, a negative electrode isformed from inside the sphere at a desired position, unnecessary nitridefilms are removed, wires are connected to the IC electrodes, and in thisway this embodiment is completed. Reference numeral 3101 denotes thespherical semiconductor substrate and 3401 denotes the selection mask.

Mounting

A mounting example is shown in FIG. 25. In FIG. 25, reference numeral3601 denotes a substrate of PMMA, etc., and 3602 denotes the opticalwaveguide core layer made of polyimide, etc. formed thereon. The cladlayer such as of PMMA is further formed thereon. A cavity is formed onthe clad layer 3603 and core layer 3602 using photolithography, etc. sothat the above-described spherical optoelectronic device can fittherein. After this, the device is fixed with UV-hardened resin, etc.(not shown). Then, contact with the printed wiring 3501 is made usingthe Au bump 3502.

Principle of Operation

Then, the principle of operation will be explained.

In Case of Light Emitting Element

In FIG. 20 or FIG. 21, the electric signal supplied from the driver IC3102 causes the light emitting element 3103 to generate an opticalsignal. This optical signal is emitted as output light to the mountedcore layer. Since the element is directly optically coupled with thecore layer, the light emitting element can efficiently guide light tothe optical waveguide.

When the light signal is desirably emitted in all two-dimensionaldirections, it is possible to simultaneously modulate the same signalsand output an optical signal. In the actual case, four directions areused, but since this light emitting element is an LED and itsdirectivity is weak, light propagates with a substantially uniformstrength distribution in all directions. To obtain a more uniformstrength distribution, it is possible to form the light emitting elementin higher-degree planar directions than the (111) equivalent plane.Then, the emitted light propagates through the two-dimensional opticalwaveguide and thereby transmits its optical signal to thisoptoelectronic device.

In Case of Light Receiving Element

This embodiment can also be used as a light receiving element. In FIG.20 or FIG. 22, a reverse bias (e.g., 3.3 V) is applied to the pnjunction of the optoelectronic device by the bias circuit 3301. At thistime, this optoelectronic device can receive an optical signalpropagating through the two-dimensional optical core layer 3106 in anarbitrary direction. This is because the light receiving surface isspherical. The input signal is taken in, absorbed near a reverse-biasedpn junction and converted to an electronic signal. The convertedelectric signal is amplified (or attenuated) by an adjacent preamp 3102to the CMOS logic level, further processed by the waveform shapingcircuit 3102, etc. and transmitted to the printed wiring contacted by abump.

Effects

This embodiment has the following effects:

-   (1) It is possible to receive light from arbitrary two-dimensional    direction.-   (2) It is possible to carry out amplifying or waveform-shaping by an    integrated electronic circuit.-   (3) It is possible to easily carry out mounting.-   (4) The influence on existing electronic circuits can be reduced,    and a single device can be used as an optical interconnection I/O.    Embodiment 9: III-VN on Ball GaAs

This embodiment uses a spherical GaAs substrate instead of a sphericalSi substrate. GaInNAs provides lattice matching with GaAs and thereforethis embodiment has a feature of allowing easier band gap control thanin the case of using an Si substrate. The method of producing it will beexplained using FIG. 24.

Production of Ball IC

As shown in FIG. 21, an IC 3102 is produced on a part of the undopedspherical Si substrate 1 mm) 3101, for example, the hemisphericalsurface (here, northern hemisphere). This IC may be a drive IC orparallel-serial conversion circuit in the case of a light emittingelement, and it may be a bias circuit. preamp, waveform shaping circuitor serial-parallel conversion circuit in the case of a light receivingelement. Of course, when the IC is used for both functions, appropriateelectronic circuits need to be added. These circuits can be made througha normal FET or Bipolar process. In FIG. 24, reference numeral 3101denotes a spherical semiconductor substrate; 3501, a buffer layer; 3502,a clad layer: 3505, a contact layer: 3506, an electrode: 3507, a window3401, a selection mask.

Production of Optical Device

After the GaAs ball IC process is almost completed, an optical device isproduced. First, the entire sphere is covered with a nitride film, etc.and the region where the optical device is made is ground or polished toform a smooth surface. The sphere is covered with the nitride film toprotect the electronic device during the optical device process and tobe used as a selective growth mask. It is desirable to form a film withsmall stress to cover the spherical surface. As the region for producingthe optical device, this embodiment uses plane (111) in the southernhemisphere and planes associated therewith (four planes in total; (100),(010), (−100), (0-10)) 3301 (triangular plane of approximately 20 μm perside). FIG. 22 is a plan view of FIG. 21 viewed from the S-pole of thesphere. FIG. 23 is a sectional view of one of these planes. The entiresurface may be covered with a nitride film, etc. again if necessary, anda window is made only in the region for producing the device. Sinceselective growth takes place according to the shape of the opening, thisembodiment controls the opening so that it becomes cylindrical. Here,the (111) equivalent plane is selected for the following reasons.

-   (1) Because they are chemically equivalent to each other, it is    possible to make a uniform structure in the subsequent crystal    growth. (If another crystalline plane is included, anisotropy occurs    in aspects of composition, film thickness and direction of crystal    growth.-   (2) In the plane contacting S-pole (in the light propagation    direction), light is emitted in at least four directions or light is    received from at least four directions. This is not limited to    the (111) equivalent plane provided that other planes have an    equivalent function or higher function.)    Crystal Growth

The structure of the device will be explained using FIG. 24. First, GaAsis stacked as a buffer layer 3501 on only a selected region (openingpart) using a gas source MBE (molecular beam epitaxy) method or MOCVD(metal-organic chemical vapor deposition) method. Then, InGaAs isfurther stacked while changing gradually the In composition so that itprovides lattice matching with In_(0.1)Ga_(0.9)As. After this, then-InAlGaAs clad layer 3502, GaInNAs/InAlGaAsMQW (Multiple Quantum Well)active layer (light emitting wavelength: 1.3 μm) 3503, p-InAlGaAs cladlayer 3504 and p-InGaAs contact layer 3505 are stacked one afteranother. Since in this crystal growth process the elements belonging tothe III-V groups of the periodic table are stacked on each other, it ischaracterized in that it is easier than the staking the elementsbelonging to the III-V groups on Si in Embodiment 8. Then, a positiveelectrode 3506 is formed after a light input/output window 3507 isattached. Then, a negative electrode is formed from inside the sphere ata desired position, unnecessary nitride films are removed, wires areconnected to the IC electrodes, and in this way this embodiment iscompleted.

Mounting

A mounting example is shown in FIG. 25. In FIG. 25, reference numeral3601 denotes a substrate made of PMMA, etc., and 3602 denotes theoptical waveguide core layer made of polyimide, etc. formed thereon. Ontop of this, a clad layer 3603 such as of PMMA is further formed. Acavity is formed on this clad layer 3603 and core layer 3602 usingphotolithography, etc. so that the above-described sphericaloptoelectronic device can fit therein. After this, the device is fixedwith UV-hardened resin, etc. (not shown). Then, contact with the printedwiring 3501 is made using the Au bump 3502.

Principle of Operation

An operation of this embodiment as a light receiving device is the sameas the case with the above-described embodiment. That is, by applying areverse bias to the optical device, the light incident upon the incidentlight window from a wide range of angles is absorbed by the pn junctionand taken in as an electric signal by an adjacent electronic device.Since Ga(In)NAs has a smaller band gap than GaAs, Ga(In)NAs operates ona lower voltage than GaAs. Furthermore, Ga(In)NAs has a greater mobilitythan Si, and can therefore respond fast.

Since Ga(In)NAs is a direct transition type compound semiconductor, itcan also be used as a light emitting element. When Ga(In)NAs is operatedas a light emitting element, by applying a forward bias to the driveelectrode of the light emitting element in FIG. 20 or FIG. 22, the lightemitted from the pn junction is emitted from the light emitting windowin a wide range of angles. This may be driven by the logic data itselfor driven through a driver circuit. Since the surface of both the lightemitting device and light receiving device is spherical, this embodimenthas a major feature of being capable of emitting and receiving light ina wide range of angles.

Effects

This embodiment has the following effects.

-   (1) It is possible to receive light with a longer wavelength than    GaAs.

When a light source with a 0.85 μm band is used, Si-pin PD of Embodiment1 may not have sufficient light receiving sensitivity. This embodimenthas no such a possibility. This also reduces burden on the electriccircuit.

-   (2) CMOS cannot be used, but an FET or GaAs bipolar circuit can be    used instead, and is therefore advantageous in high-speed    processing.-   (3) By using high-speed processing capability, it is possible to    convert parallel data to serial data and then transfer.-   (4) In this structure, GaAsN is a direct transition type, and    therefore can also be used as a light emitting element.

This embodiment uses a spherical GaAs substrate, but this embodiment isnot limited to this substrate.

Embodiment 10: III-VN on Spherical InP Substrate

Using a spherical InP substrate for the substrate makes it possible toobtain other effects.

This embodiment will be explained using FIG. 24 again.

Production of Ball IC

As shown in FIG. 21, an IC 3102 is produced on the hemispherical surface(here, northern hemisphere) of the undoped spherical lnP substrate (1mm) 3101. This IC may be a drive IC or parallel-serial conversioncircuit in the case of a light emitting element, and the IC may be abias circuit, preamp, waveform shaping circuit or serial-parallelconversion circuit in the case of a light receiving element. Of course,when the IC is used for both functions, appropriate electronic circuitsneed to be added. These circuits can be made through a normal FET orBipolar process. Since it has a smaller band gap and a higher mobilitycompared with GaAs, it is possible to use a high-speed driver circuit.

Production of Optical Device

After the InP ball IC process is almost completed, an optical device isproduced. First, the entire sphere is covered with a nitride film, etc.and the region where the optical device is made is ground and polishedto form a smooth surface. The sphere is covered with the nitride film inorder to protect the electronic device during the optical device processand to be used as a selective growth mask. It is desirable to form afilm with small stress to cover the spherical surface. As the region forproducing the optical device, this embodiment uses plane (111) in thesouthern hemisphere and planes associated therewith (four planes intotal; (100), (010), (−100), (0-10)) 3301 (triangular plane ofapproximately 20 μm per side). FIG. 22 is a plan view of FIG. 21 viewedfrom the S-pole direction. FIG. 23 is a sectional view of one of theseplanes. The entire surface may be covered with a nitride film, etc.again if necessary and a window is made only in the region for producingthe device. Since selective growth takes place according to the shape ofthe opening, this embodiment controls the opening so that it becomescylindrical. Here, the (111) equivalent plane is selected for thefollowing reasons.

-   (1) Because they are chemically equivalent to each other, it is    possible to make a uniform structure in the subsequent crystal    growth. (If another crystalline plane is included, anisotropy occurs    in aspects of composition, film thickness and direction of crystal    growth.)-   (2) In the plane contacting S-pole (in the light propagation    direction), it is possible to emit light in at least four directions    or receive light from at least four directions. This is not limited    to the (111) equivalent plane provided that other planes have an    equivalent function or higher function.)    Crystal Growth

The structure of the device will be explained using FIG. 24. First, InPis stacked as a buffer layer 3501 on only a selected region (openingpart) using a gas source MBE (molecular beam epitaxy) method or MOCVD(metal-organic chemical vapor deposition) method. Then, InGaP is furtherstacked thereon while changing gradually the In composition so that itprovides lattice matching with In_(0.9)Ga_(0.1)P. After this, then-InAlGaP clad layer 3502, GaInNP/InAlGaPMQW (Multiple Quantum Well)active layer (light emitting wavelength: 1.5 μm) 3503, p-InAlGaP cladlayer 3504 and p-InGaP contact layer 3505 are stacked one after another.After the light input/output window 3507 is attached, a positiveelectrode 3506 is formed. Then, a negative electrode is formed frominside the sphere at a desired position, unnecessary nitride films areremoved, wires are connected to the IC electrodes, and in this way thisembodiment is completed.

Mounting

A mounting example is shown in FIG. 25. In FIG. 25, reference numeral3601 denotes a substrate made of PMMA, etc., and 3602 denotes theoptical waveguide core layer made of polyimide, etc. formed thereon. Ontop of this, a clad layer 3603 such as of PMMA is further formed. Acavity is formed on this clad layer 3603 and core layer 3602 usingphotolithography, etc. so that the above-described sphericaloptoelectronic device can fit therein. After this, the device is fixedwith UV-hardened resin, etc. (not shown). Then, contact with the printedwiring substrate 3605 is made using the Au bump 3606. The referencenumeral 3604 denotes an electrode.

Principle of Operation

In the case of an operation as a light receiving device, by applying areverse bias to the optical device, the light incident upon the incidentlight window from a wide range of angles is absorbed by the pn junctionand taken in as an electric signal by an adjacent electronic device.Since InGaPN has a smaller band gap than InP, InGaPN operates on a lowervoltage than InP. Furthermore, InGaPN has a greater mobility speed thanSi, and can therefore respond fast. Since InGaPN is a direct transitiontype compound semiconductor, it can also be used as a light emittingelement. When InGaPN is operated as a light emitting element, byapplying a forward bias to the optical device in FIG. 20 or FIG. 22, thelight emitted from the pn junction is emitted from the light emittingwindow in a wide range of angles. This may be driven by the logic dataitself or driven through a driver circuit. The surfaces of both thelight emitting device and light receiving device are spherical, thisembodiment has a major feature of being capable of emitting andreceiving light in a wide range of angles.

Effects

This embodiment has the following effects.

-   (1) Use of a small band gap has smaller burden on the electric    circuit.-   (2) It is possible to produce a faster circuit than Si or GaAs.-   (3) Because 1.5 μm band light can be used, it is possible to    directly couple with a low loss fiber without any relay circuit and    carry out long-distance high-speed transmission.    Embodiment 11: III-VN on GaN Substrate

Using a spherical GaN substrate for the substrate makes it possible toobtain other effects.

This embodiment will be explained using FIG. 24 and others again.

Production of Ball IC

As shown in FIG. 21, an IC 3102 is formed on the hemispherical surface(here, northern hemisphere) of the undoped spherical GaN substrate (1mm) 3101. This IC may be a drive IC or parallel-serial conversioncircuit in the case of a light emitting element, and the IC may be abias circuit, preamp, waveform shaping circuit or serial-parallelconversion circuit in the case of a light receiving element. Of course,when the IC is used for both functions, appropriate electronic circuitsneed to be added. These circuits can be made by combining a normal FETor Bipolar process (e.g., S. C. Binari, K. Doverspike, G. Kelner H. B.Dietrich, and A. F. Wickenden; Solid State Electronics, 41(1997). p. 97or S. Yoshida and J. Suzuki; Journal of Applied Physics Letters, 85(1999). p. 7931, etc.) and spherical Si process (see Embodiment 8. Sinceits band gap is by far larger than Si, and has therefore performanceindices different from Si and other III-V materials such as capabilityof high temperature, high voltage and high frequency operations.

Production of Optical Device

After the GaN ball IC process is almost completed, an optical device isproduced. First, the entire sphere is covered with a nitride film (SiN,etc.) and the region where the optical device is made is ground andpolished to form a smooth surface. The sphere is covered with thenitride film in order to protect the electronic device during theoptical device process and to be used as a selective growth mask. It isdesirable to form a film with small stress to cover the sphericalsurface. As the region for producing the optical device, this embodimentuses plane (111) in the southern hemisphere and planes associatedtherewith (four planes in total; (100), (010), (−100), (0-10)) 3301(triangular plane of approximately 20 μm per side). FIG. 22 is a planview of FIG. 21 viewed from the S-pole direction. FIG. 23 is a sectionalview of one of these planes. The entire surface may be covered with anitride film, etc. again if necessary and a window is made only in theregion for producing the device. Since selective growth takes placeaccording to the shape of the opening, this embodiment controls theopening so that it becomes cylindrical. Here, the (111) equivalent planeis selected for the following reasons.

-   (1) Because they are chemically equivalent to each other, it is    possible to make a uniform structure in the subsequent crystal    growth. (If another crystalline plane is included, anisotropy occurs    in aspects of composition, film thickness and direction of crystal    growth.)-   (2) In the plane contacting S-pole (in the light propagation    direction), it is possible to emit light in at least four directions    or receive light from at least four directions. This is not limited    to the (111) equivalent plane provided that other planes have an    equivalent function or higher function.)    Crystal Growth

The structure of the device will be explained using FIG. 24. First, GaNis stacked as a buffer layer 3501 on only a selected region (openingpart) using a gas source MBE (molecular beam epitaxy) method or MOCVD(metal-organic chemical vapor deposition) method. Then, the n-AlGaN cladlayer 3502, GaInN/AlGaNMQW (Multiple Quantum Well) active layer (lightemitting wavelength: 0.4 μm) 3503, p-AlGaN clad layer 3504 and p-GaNcontact layer 3505 are stacked one after another. After the lightinput/output window 3507 is attached, a positive electrode 3506 isformed. Then, a negative electrode is formed from inside the sphere at adesired position, unnecessary nitride films are removed, wires areconnected to the IC electrodes, and in this way this embodiment iscompleted.

Mounting

A mounting example is shown in FIG. 25. In FIG. 25, reference numeral3601 denotes a substrate such as of PMMA and 3602 denotes the opticalwaveguide core layer made of polyimide, etc. formed thereon. On top ofthis, a clad layer 3603 such as of PMMA is further formed. A cavity isformed on this clad layer 3603 and core layer 3602 usingphotolithography, etc. so that the above-described sphericaloptoelectronic device can fit therein. After this, the device is fixedwith UV-hardened resin, etc. (not shown). Then, contact with the printedwiring 3605 is made using the Au bump 3606.

Principle of Operation

In the case of an operation as a light receiving device, it iscompletely carried out in the same manner as in the case of Embodiment8. That is, by applying a reverse bias to the optical device, the lightincident upon the incident light window from a wide range of angles isabsorbed by the pn junction and taken in as an electric signal by anadjacent electronic device. Since GaN has a much smaller band gap thanSi, GaAs or InP, GaN requires a high voltage. On the other hand, it hasan advantage that it is capable of high temperature operation for boththe electronic device and optical device. When GaN is operated as alight emitting element, by applying a forward bias to the optical devicein FIG. 20 or FIG. 22, the light emitted from the pn junction is emittedfrom the light emitting window in a wide range of angles. This may bedriven by the logic data itself or driven through a driver circuit.

Since the surfaces of both the light emitting device and light receivingdevice are spherical, this embodiment has a major feature of beingcapable of emitting and receiving light in a wide range of angles.

This embodiment has the following effects.

-   (1) Because of a large band gap, it is possible to operate at a high    temperature.-   (2) High voltage operation can be carried out compared with Si and    GaAs.-   (3) Because 0.4 μm band light can be used, ON/OFF can be confirmed    by naked eyes.    Embodiment 12: Single Layer Electric Wiring Layer+Optical Wiring    Layer+Photonic Ball IC

FIG. 26 is a schematic view for illustrating another embodiment of thepresent invention.

In FIG. 26, reference numeral 4101 denotes a support substrate; 4107 and4108, an optical wiring layer and electric wiring layer formedthereupon. Reference numeral 4102 denotes an IC chip mounted on anelectric wiring layer 4107.

FIG. 27 is an enlarged view of the portion 27 of FIG. 26 and referencenumeral 4103 denotes a bump for mounting the IC 4102 (e.g., ballsolder); 4104 a photonic ball; 4105, an electrode pad for electricallyconnecting these components. 4106 and 4109 denote a two-dimensionaloptical waveguide (hereinafter referred to as “optical film”) and cladlayer that make up an optical wiring layer 4108. This configuration isreferred to as a “optoelectronic substrate”.

In this embodiment, when the IC chip 4102 is connected to an electricwiring layer 4107, a plurality of metal bumps are used (FIG. 26). A partof the metal bumps is replaced with photonic ball ICs 4104 of almost thesame size. A part of photonic ball ICs 4104 are embedded in the opticalwiring layer 4108.

When the optical wiring layer 4108 is formed, it is set that thesubstrate 4111 is 0.5 mm thick, the core layer 4106 is 0.1 mm thick andthe clad layer 4109 is 0.3 mm thick, but they are not limited to thesesizes. The clad layer may be omitted.

For the electric wiring layer 4107, it is possible to use a thermalfusion type resin material (0.3 mm thick) with a built-in single-layerCu micro strip line 4110.

Photonic Ball IC

One of the features of the present invention is that the IC chip ismounted on the optoelectronic board through an EO or OE device.

Then, the photonic ball IC, which is an example of this EO or OE device,will be explained in short below (its production method is described,for example, in Japanese Patent Application Laid-Open No. 2001-284635).

In FIG. 28, reference numeral 4201 denotes an undoped spherical Sisubstrate (e.g., 1 mm): 4202, an IC formed on the hemispherical surface(here, northern hemispherical surface). Reference numeral 4203 denotesan optical device such as a light emitting element or light receivingelement formed on the southern hemispherical surface there, it ispossible to use a GaInNAs AlGaAs-based planar light emitting laser orplanar photodiode formed or the four planes equivalent to (111)).Reference numeral 4204 denotes an electric wire.

When integrated with the light emitting element 4203, the IC 4202 may bea drive IC or parallel-serial conversion circuit. When integrated withthe light receiving element 4203, the IC 4202 may be a bias circuit,preamp, waveform shaping circuit or serial-parallel conversion circuit.Of course, when the IC is used for both functions, appropriateelectronic circuits need to be added. These circuits can be made througha normal CMOS process and its logic voltage is 3.3 V.

FIG. 29 shows another mode of the photonic ball IC. In FIG. 29, theelectronic circuit is the same as above, but the optical device is verydifferent. Reference numeral 4305 is a hemispherical active layer and inthe case of a light emitting device, carriers injected from the opticaldevice electrode 4307 re-couple and emit light. In the case of a lightreceiving device, a reverse bias is applied to the active layer 4305 andthe received light forms an electron-hole pair. The active layer 4305 isspherical in both cases, and therefore it is possible to perform EO orOE conversion with high efficiency without preparing any special opticalsystem.

Mounting Photonic IC on Optoelectronic Board

Then, the method of mounting this spherical optical device will beexplained. First, a hemispherical cavity is made on the surface of theoptoelectronic board (the electric wiring layer 4107 in this embodiment)to allow the above-described photonic ball IC to fit therein.

The method of making the cavity is the same as that described above.

Then, the optical device is mounted in the cavity of the optical sheetin such a way that the optical device comes to the bottom side. To allowlight to be taken in or out, the optical device is positioned and fixedin such a way that the optical I/O section touches the bottom of thecavity (see FIG. 30). After the positioning, the optical device can befixed with UV-hardened resin, etc.

Then, electrical connections are made using a flip chip mounting method.In FIG. 30, reference numeral 4103 denotes a bump and 4105 denotes anelectrode pad. The bump is placed on the electrode pad 4105 on the ICside, the above-described photonic ball IC 4104 is positioned with thesubstrate, the bump is melted by reflow and then cooled down, thusmaking it possible to obtain an electrical contact all at once.

Thus, performing flip chip mounting and photonic ball IC mountingsimultaneously not only simplifies processes but also increasesmechanical strength of the photonic ball IC.

Here, the bump is assumed to be rectangular but it is not necessary tostick to this form. Finally, the gap between the IC chip andoptoelectronic board is filled with a refilling material, etc. (notshown), which creates a more stable mounting condition. Of course, it isalso possible to mount BGA (Ball Grid Array) on the bump using ballsolder.

Principle of Operation

Then, the principle of operation will be explained.

Transmission Function

In FIG. 30, the electrode pad 4105 of the LSI 4102 can send or receive asignal to or from adjacent electronic devices via the bump 4104. The LSIlogic signal (e.g., 3.3 V in the case of CMOS) is a voltage enough todirectly drive the above-described spherical optical device.

Applying a logic signal, which constitutes a forward bias, to a lightemitting device (e.g., LED) on the photonic ball IC 4104 causes theelectric signal to convert to an optical signal (when power is requiredor when a predetermined bias voltage should be applied, a driver circuitor bias may be built in on the photonic ball IC). The emitted light isoutput to the core layer 4106 and spreads and propagates over the entireoptical sheet as the output light 4109 without any special opticalsystem. If the size of the substrate is about 30 mm per side andpropagation loss is 0.3 dB/cm or less, light output of about 1 mW isenough to obtain reception input necessary for minimum receptionsensitivity.

Reception Function

On the contrary, when the input optical signal 4110 that propagatesthrough the optical wiring layer (optical film) 4108 in an arbitrarydirection reaches the surface of the light receiving element 4102 of thephotonic ball IC, it is taken in, absorbed near a reverse-biased pnjunction and converted to an electronic signal. The converted electricsignal is taken in the adjacent LSI 4102 as an input electronic signaland processed by the adjacent LSI 4102.

Electric Parallel/Optical Serial Transmission

Electric parallel/optical serial transmission will be explained usingFIG. 31. In FIG. 31, reference numeral 4601 denotes an optoelectronicboard; 4602 and 4608, CPUs; 4603, a RAM shared by these two CPUs; 4604,other devices; 4605, electric wiring; 4606, optical wiring.

Normal electric wiring requires, for example, 64-bit data lines with 6transmission paths. There is no problem with low-speed data processing,whereas an application involving large-volume and high-speed datatransfer (moving images, etc.) is susceptible to influences fromoperations of other devices mounted on the substrate or influences ofEMI. It is extremely difficult for conventional wiring to constantlysend stable data. Optical wiring is used only for such an application.

For example, in FIG. 31, 6 electric wires are necessary to send 64-bitdata from the CPU 4602 to RAM 4603, but if parallel-serial conversion isperformed at the final stage of the CPU and one optical I/O element isconnected, an electric signal is sent as an optical signal through theoptical waveguide section of the optoelectronic board, received by theoptical I/O element on the receiving side and serial-parallel convertedinto a 64-bit parallel signal. The parallel-serial conversion increasesthe clock but there is no problem of EMI because the signal propagatesthrough the optical waveguide.

Use of a flip chip mounting or BGA method as the mounting methodprovides an easy way of mounting without applying an additional mountingmethod for optical wiring. The BGA (Ball Grid Array) method is a methodof connecting an IC electrode pad and substrate electrode pad in arrayform using solder called “bump” and has excellent characteristics suchas faster operation, smaller area occupied and lower resistance comparedto conventional wire bonding.

Typical sizes of BGA pitch and ball solder are about 1 mm and 0.50 mmrespectively. That is, if the above-described photonic ball IC is 1 mmor below, it is possible to use a normal BGA process.

The photonic ball IC consists of an electronic device and optical deviceintegrated on a spherical semiconductor substrate (usually spherical Sisubstrate), and this photonic ball IC alone can perform OE/EOconversions. Using a photonic ball IC that can be directly driven withthe voltage of a logic signal from an LSI on the optoelectronic boardrequires no special additional circuit. Because it is spherical, thephotonic ball IC can also be optically coupled with the optical filmsection of the above-described optoelectronic board without requiringany special optical system.

Embodiment 13: Changing Sequence of Electric Wiring Layer and OpticalWiring Layer

FIG. 32 is a schematic view for illustrating another embodiment of thepresent invention. This embodiment differs from Embodiment 12 in thatthe electric wiring layer consists of multiple layers and the opticalwiring layer is stacked thereon.

In FIG. 32, reference numeral 4107 denotes an electric wiring layercontaining multi-layer internal wiring 110, and reference numeral 4108denotes an optical wiring layer (optical film) composed of the corelayer 4106 and clad layers 4109 and 4111.

On the outermost surface of the optical wiring layer, an electrode pad4105 and wiring pattern (not shown) are arranged, and the electricwiring layer 4107 is coupled through a via hole 4110. This via holepenetrates the optical wiring layer and since light propagatestwo-dimensionally, there is little influence unless the via is denselyformed.

An effect specific to this embodiment is that the optical wiring layercan be placed independently of the thickness of the electric wiringlayer.

Embodiment 14: Inserting Two Optical Sheets in a Multi-layer PCBSubstrate

FIG. 33 is a schematic view for illustrating another embodiment of thepresent invention. This embodiment differs from Embodiment 12 in thatnot only an electric wiring layer but also an optical film are formed onboth sides.

In FIG. 33, reference numeral 4101 is a support substrate and thestructure in Embodiment 13 is formed on both sides of the supportsubstrate. Furthermore, forming a via hole 4111 that penetrates thesupport substrate 4101 allows both sides to be electrically connected.Other processes are the same as those in Embodiment 12 or Embodiment 13.

As a special case, the support substrate 4101 may be removed.

FIG. 34 is a schematic view illustrating this embodiment.

The optoelectronic board consists of a pair of optical wiring layers(4108) and one multi-layer wiring layer (4107). Use of flexiblematerials for both the multi-layer wiring layer and optical wiring layerprovides an optoelectronic flexible board.

Features of this configuration are not only that the mounting area canbe increased but also that it is possible to provide EMI-free opticalwiring using an optical film in such a situation that wires in themulti-layer wiring layer are close to each other and EMI is notnegligible, and that removing the support substrate provides a moreflexible substrate. For example, it is also possible to bend thesubstrate itself 90 degrees and mount it.

As described above, the present invention can provide a semiconductordevice having reduced direction dependency when light propagatingthrough the optical transmission region (optical sheet) is received.

1. A semiconductor device in a printed board comprising: an opticaltransmission region for transmitting a light signal; and a lightemitting part; and a light receiving part for converting the lightsignal propagating through the optical transmission region to anelectrical signal, wherein the optical transmission region comprises atwo-dimensional optical waveguide layer capable of propagating the lightsignal in a plurality of directions, wherein at least a portion of thelight receiving part is embedded in the optical transmission region suchthat the light receiving part can receive the light signal propagatingwithin a plane of the two-dimensional optical waveguide layer, andwherein the at least a portion of the light receiving part has aspherical surface.
 2. The semiconductor device according to claim 1,wherein an electric wiring layer is stacked on the optical transmissionregion.
 3. The semiconductor device according to claim 1, wherein the atleast a portion of the light receiving part is embedded in the opticaltransmission region such that the light receiving part can directlyreceive the light signal propagating through the two-dimensional opticalwaveguide layer.
 4. The semiconductor device according to claim 1,wherein the light receiving part includes a spherical device.
 5. Thesemiconductor device according to claim 1, wherein the light emittingpart is for transmitting the light signal to the optical transmissionregion, and wherein at least a portion of the light emitting part isembedded in the optical transmission region.
 6. The semiconductor deviceaccording to claim 2, wherein the optical transmission region isinterposed between the electric wiring layer located on the opticaltransmission region and another electric wiring layer located under theoptical transmission region, and wherein at least a portion of theelectric wiring layer is electrically connected to at least a portion ofthe another electric wiring layer by a via hole for penetrating theoptical transmission region.
 7. The semiconductor device according toclaim 2, wherein at least one of O/E conversion or E/O conversionbetween an electronic device provided on the electric wiring layer andthe optical transmission region is performed using a spherical device.8. An optoelectronic printed board comprising: a substrate comprising atleast a first layer and a second layer, the first layer including anelectronic device, an optical device, a light emitting device, and anelectric wiring for coupling the electric device and the optical device,and the second layer including a two-dimensional optical waveguidecapable of propagating a light signal in a plurality of directions,wherein the optical device comprises a light receiving part forreceiving the light signal waveguided through the two-dimensionaloptical waveguide, wherein at least a portion of the light receivingpart is embedded in the two-dimensional optical waveguide such that thelight receiving part can receive the light signal propagating within aplane of the two-dimensional optical waveguide, and wherein the lightreceiving part has a spherical structure, the light receiving part ismounted from a surface of the substrate such that the at least a portionof the light receiving part is embedded in the two-dimensional opticalwaveguide, and the light receiving part is coupled, on the surface ofthe substrate, with the electric wiring.
 9. The optoelectronic printedboard according to claim 8, wherein the two-dimensional opticalwaveguide has a sheet-shaped form.
 10. The optoelectronic printed boardaccording to claim 8, wherein the optical device is provided with anelectric circuit for driving the light receiving part or amplifying anelectric signal obtained.
 11. The optoelectronic printed board accordingto claim 8, wherein a light source of the optical device has a sphericalshape, the light source is mounted on the substrate from a surface ofthe substrate such that at least a portion of the light source isembedded in the two-dimensional optical waveguide of the substrate, andthe light source is coupled, on the surface of the substrate, with theelectric wiring.
 12. The optoelectronic printed board according to claim8, the substrate further comprising: a transmission device fortransmission having a spherical structure; and a parallel signal line,wherein an output terminal of the parallel signal line is coupled withthe transmission device for transmission, and wherein the transmissiondevice for transmission conducts parallel/serial conversion and sends aserial optical signal to the two-dimensional optical waveguide.
 13. Theoptoelectronic printed board according to claim 12, wherein the serialoptical signal is received by the light receiving part, converted to anelectric signal, subjected to serial/parallel conversion by anelectronic circuit simultaneously formed on the light receiving part,and transmitted to the parallel signal line.
 14. The optoelectronicprinted board according to claim 8, wherein the optoelectronic printedboard is made of a flexible substrate material.
 15. An optoelectronicintegrated circuit comprising: an electronic device and optical deviceintegrated on a surface of a spherical semiconductor substrate, whereinthe optical device is a light receiving element that includes amulti-layer film containing a pn junction, and wherein the electronicdevice includes at least a bias circuit for applying a reverse bias tothe light receiving element, and an amplifier for amplifying a signalobtained by converting a received light to an electric signal.
 16. Theoptoelectronic integrated circuit according to claim 15, wherein atleast a portion of the light receiving element is embedded in an opticaltransmission medium.
 17. The optoelectronic integrated circuit accordingto claim 15, wherein the spherical semiconductor substrate is made of anSi single crystal.
 18. The optoelectronic integrated circuit accordingto claim 15, wherein the spherical semiconductor substrate is made of aGaAs single crystal.
 19. The optoelectronic integrated circuit accordingto claim 15, wherein the multi-layer film of the light receiving elementis made of p-Si, i-Si and n-Si.
 20. The optoelectronic integratedcircuit according to claim 15, wherein the multi-layer film of the lightreceiving element is made of p-GaAs, GaAsN and n-GaAs.
 21. A method ofproducing the optoelectronic integrated circuit according to claim 15,which comprises forming the multi-layer film of the light receivingelement by ion implantation.
 22. An optoelectronic integrated circuitcomprising: an electronic device and optical device integrated on asurface of a spherical semiconductor substrate, wherein the opticaldevice is a light emitting element that includes a multi-layer filmcontaining a pn junction in a radial direction of the sphericalsemiconductor substrate, and wherein the electronic device comprises abias circuit that applies a forward bias to the light emitting element.23. The optoelectronic integrated circuit according to claim 22, whereinat least a portion of the light emitting element is embedded in anoptical transmission medium.